1. Field of the Invention
The present invention relates to a vertical type continuous casting apparatus and more particularly to a vertical type continuous casting apparatus which comprises a movable hood for discharging iron oxide sludge and combustion gases generated when a continuous cast strand is cut by gas at the lower portion of the apparatus and a divisional dummy bar is used when continuous casting operation begins.
2. Description of the Prior Art
In the vertical type continuous casting apparatus, a continuous cast strand moved down by pullout pinch rolls within a lower caisson is cut by a gas cutting machine to deliver the cut cast strand by means of an ejecting device. In the gas cutting machine, high pressure oxygen is blown mainly towards a high temperature continuous cast strand to cut it by oxidization, and therefore a cut width of about 10 to 15 mm, which differs with the dimension of a torch, is produced. This cut width portion is formed into an iron oxide scale, which is blown off to generate sludge.
In the past, a vertically lengthy, open, fixed hood is provided over the entire width of a vertically moving stroke of the gas cutting machine so as to recover generated sludges. The hood is communicated with a duct for discharging, by a suction blower, gases generated as cutting takes place. However, since the open area of the hood is large, the capacity of the blower needs to be increased. In addition, the efficiency of recovery of the sludge is not sufficient and a part of the sludge is scattered and accumulated in the periphery so as to impair the operation of devices located lower, and, therefore, continuous operation has to be suspended for cleaning. This results in an unavoidable reduction in productivity, particularly in case of so-called continuous casting in which casting from a plurality of ladles is possible so as to allow for continuous casting. The conventional fixed hood is not only low in performance but high in manufacturing cost, resulting in an increase in construction cost of the continuous casting apparatus.
Moreover, it is necessary that when continuous casting operation begins, a bar having the same sectional shape as that of a product and which is called a dummy bar is placed on a bottom of a mould to remove molten metal while being integrally attached to the dummy bar to continue the casting operation.
Where the dummy bar is of an integral type and a lower insertion system is used as a system for inserting a dummy bar into a water-cooled mould, an underground pit, called a caisson is used, whereas where an upper insertion system is used, a house and a crane become highly elevated. Each system requires a relatively high cost of equipment.
One solution is to use a divisional dummy bar so that these sections may be removed successively. However, in the vertical type continuous casting, a dummy bar is downwardly inserted into a mould by plural groups of pinch rolls and the weight of a continuous cast strand and the weight of the dummy bar are balanced to remove the continuous cast member from the mould, and therefore, the division itself of the dummy bar is restricted in terms of relation with the pinch rolls. Furthermore, with respect to means for connecting the divisional dummy bar, there is posed a problem in terms of difficulty in construction to meet requirements, at the same time, such as positive passage of the dummy bar through roll portions, and positive connection to prevent unexpected disengagement when an easy disengagement feature is necessary. Therefore, there have been disadvantages in that the continuous casting apparatus increases in scale and equipment costs also increase.